| Colourimetric detection of metal ion is very sensitive, rapid, and simple to-use method. It is very important both from industrial as well as biological point of view. In this paper, a series of carbazole derivatives,4-(9-Carbazole) benzoic acid methyl ester (Cl),4-[(3-bromide)-carbazole] benzoic acid methyl ester (C2) and 4-(3-(5’-methyl acyl thiophene)-9 carbazole) benzoic acid methyl ester (C3) were synthesized, and their structures were characterized. Further,methyl-4-(3-(5-((Z)-(((Z)-2-amino-1,2-dicyanovinyl) imino)methyl) thiophen-2-yl)-9 H-carbazol-9-yl) benzoate (L1) and methyl (E)-4-(3-(5-(((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl) imino) methyl) thiophen-2-yl)-9H-carbazol-9-yl)benzoate (L2) were synthesized for colourimetric detection of metal ion. The schiff base of (E)-2,3-dimethyl-4-((2-(4-methylpyridin-2-yl)pyridin-4-ylimino)methyl)-1 phenyl-1,2-dihydropyrazol-5-one (L3) was synthesized and characterized. The main results obtained are as follows:(1) The compound Cl was synthesized by introducing a substituted methyl benzoate in carbazole site 9. The compounds C2 and C3 were synthesized by introducing substituent corresponding the carbazole site 3 based on Cl. The compounds L1 and L2 were synthesized by the condensation of C3 and maleonitrile and 4-aminoantipyrine. The compounds were characterized with 1HNMR, FT-IR, UV-Vis spectrum and fluorescence spectrum. The results showed that the maximum absorption peak of C1 and C2 were located at 337 nm and 344nm, respectively, in methanol solvent. The compounds Cl, L1 and L2 show the maximum absorption wavelength at 373 nm,441 nm and 407 nm in DMF solvent, respectively. The maximum emission wavelengths of Cl, C2 and C3 were 469 nm,460 nm and 470 nm, all of them were blue fluorescence. The maximum light emission wavelength of L1 and L2 were 492 and 472 nm.(2) We have investigated the effects of different metal ions on the fluorescence of L2 by using compound L2 as fluorescent probe. The results showed that the fluorescence intensity of L2 was significantly increased after the addition of Co2+. The job method was used to measure Co2+ and L2 to form a 1:1 complex. The maximum absorption peak and fluorescence emission peak of the complexes are located at 375 nm and 466 nm. Fe2+, Fe3+, Na+, K+, Ca2+, Ba2+, Mn2+, Ni2+, Hg2+, Zn2+, Cd2+, Cu2+ and other coexisting metal ions do not affect the fluorescence recognition of L2 to Co2+. The minimum detectable amount of L2 as a fluorescent probe for Co2+ recognition is:8.9×10-6 mol/L, linear range: 8.9×10-6-5×10-5 mol/L, correlation coefficient:R2=0.9911.(3) Taking the compound L3 as the color reagent, the color effect of metal ions was investigated. It is found that the Fe2+ aqueous solution by adding L3 (1×10-5mol/L) ethanol solution after the solution from colorless to red. The absorption wavelength is 547 nm. Under the same conditions, the other selected cations and anions have no color reaction. A condition for the determination of Fe2+ was established. Detection range of 9.4×10-8-1.8×10-5mol/L, the correlation coefficient R2=0.9994, the minimum detection limit of 9.4×10-8 mol/L. |
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